Crocoite

Chemical name |  Lead chromate
Chemical formula |  PbCrO4
Identification
Birefringence |  0.270
Colors |  Red-orange, cherry red, orange, yellowish
Crystal habit |  Crystals usually prismatic, striated lengthwise; also acicular, granular, columnar, incrusting, sometimes hollow
Crystal system |  Monoclinic
Cleavage |  Distinct, one direction; poor in two other directions. Brittle
Dispersion |  Strong
Fracture |  Conchoidal, uneven; brittle and sectile
Hardness |  2.5-3
Luster |  Adamantine to vitreous
Luminescence |  Weak reddish to dark brown (SW); weaker effect in LW
Name origin |  From the Greek krokos, meaning saffron, in allusion to the color
Optics |  α = 2.29-2.31; β = 2.36; λ = 2.66. Biaxial (+), 2V = 57°
Pleochroism |  Orange-red to blood red
Specific gravity |  5.9-6.1
Spectral |  Distinct band at 5550 but seen only in thin fragments. Transmits mainly in the yellow-red region of the spectrum
Streak |  Orange-yellow

## Occurrence[edit]

Secondary mineral in oxidized zones of lead deposits.
Dundas, Tasmania: best crystals found in the world, some gemmy; large clusters.
Beresov Dist., U.S.S.R.: red crystals.
Tiger, Arizona: very tiny crystals.
California
Minas Gerais, Brazil

## Comments[edit]

Crocoite is one of the loveliest of all collector stones. It's too soft and brittle for wear, but it is quite a rare mineral and relatively few stones have been cut. The dispersion is high but completely masked by the intense body color.

Arem, p. 34
Chesterman, p. 470

## Sources[edit]

* Arem, Joel E. Color Encyclopedia of Gemstones, Litton Educational Publishing, Inc.:New York (1977)
* Chesterman, Charles W. The Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf: New York (1987)